In recent years, elastic synthetic resin compositions, for example, adhesives and sealants for absorbent and nonabsorbent subsurfaces and surfaces, have gained increasingly in importance, particularly in the building industry. While "Thiokol" sealants have been utilized in earlier years to a predominant extent, silicone and polyurethane sealing compounds have found increasing use more recently.
Elastic coating, sealing, and adhesive compounds are utilized as joint sealants for the sealing of prefabricated building components and exposed concrete surfaces. They must compensate for considerable temperature-dependent movements in addition to performing the actual sealing function. During this process, stress-strain forces occur which can place a considerable load on the adhesion surface. They are also employed as adhesives and sealants in the automobile industry where they are utilized with special advantage for sealing glass to metal, for example, for the mounting of windshields, and for other purposes where metal must be glued to metal.
Stringent requirements are placed on the adhesive power as well as the curing rate of the resins in these applications.
DOS No. 2,738,979 discloses a process for the production of crosslinkable polyurethane prepolymers with end positioned alkoxysilyl groups. The prepolymers harden under the effect of moisture at room temperature into elastic products having good mechanical properties and good adhesion. However, these products have the drawback that their curing rate, particularly in the layers of .gtoreq.1 mm primarily encountered under practical conditions, does not satisfy requirements. Due to the slow skinning, the surfaces remain tacky for a long time. Dust and dirt particles can settle thereon whereby their mechanical properties as well as external appearance are impaired. Moreover, the coating seal, or adhesive bond does not attain the frequency required load-bearing capacity within practical time limits.